Geologist-Geophysicist - Perth
January 1 2005
SUMATRA BOXING DAY SEISMIC EVENT
I note that all seismic info web sites are showing large (6.0-5.0
Richter scale) quakes continuing every couple of hours along the
Andaman-Sumatra fault line. These have been occurring ever since
Boxing Day (26-12-04) right up until today (1-01-05). The continuing
quakes demonstrate VERY "noisy" high energy background seismograph
records when viewed on seismograms collected from seismic stations
located within a few thousand kilometers of the original 9.0 Richter
event. This may indicate continued high frequency micro-quakes of
the type associated with volcanic intrusion in the upper crust - on
a massive scale - along the Andaman-Sumatra island arc zone.
The IRIS and USGS web sites show the spread of recent quakes running
along some 1000km of fault line from the Andamans to
NW Sumatra. But
the European Seismic Centre at
http://www.emsc-csem.org/ has been
re-calculating the many quake epicenters and their work suggests
these quakes are (mostly) clustering around the same point - off NW
Given the violent off-scale nature of seismograms over the last few
days it is difficult to generate either precise Richter level info
OR precise Lat-Long co-ordinates for specific events. In fact the
noise level on many seismograms suggest this has been and is a
nearly continuous energy event with regular high energy peaks every
few hours. This may indicate that igneous intrusive action is
occurring here on a massive scale deep within the crust associated
with continual faulting movement along the proto island arc???
A long dormant Andaman volcano has begun to erupt over the last few
days and an Indian Government geologist has said that this eruption
is nothing to be concerned about. Many volcanoes along the
Andaman-Sumatran arc are of a highly explosive type - but I am
unfamiliar with the specific newly erupting volcano type.
If you read the information below (taken from Dr. George
Pararas-Carayannis site re the 1883 explosion of
Krakatoa) you might wish to
contest the statement that "there is nothing to be concerned about"
You should note that some 1000 years previously an exploding proto Krakatoa was literally the cause of the "DARK AGES" !!! But more
recently, in 1883, it began all over again as follows :
"After a long period of inactivity (about 200 years),
became active again in early 1883. The first indication that
something was happening on Krakatoa was when a large earthquake
struck the area. Seismic activity became stronger until May 20,1883,
when the volcano abruptly came to life. The initial explosive
eruptions of Krakatoa could be heard 160 km away. Steam and ash
could be seen rising 11km above the summit of the volcano. By August
11, 1883. three vents were actively erupting. Eleven other vents
were ejecting smaller quantities of steam, ash and dust.
Around 1 pm on the 26th of August 1883, the explosions became more
frequent occurring on the average every 10 minutes. Sailors on a
ship, 120 km away from the island reported a black cloud of smoke
rising above the volcano. At the time the rim of Krakatoa's crater
was approximately 1,000 meters in diameter and had and average depth
of 50 meters. The volcano' s central vent was blocked by a plug of
solid lava and underneath it pressure was rapidly building up.
The Great Eruption
The renewed activity in May 1883 culminated in four gigantic
explosions on August 26 and 27 of the same year. On the afternoon of
August 26, 1883, (27 August local date) at 17: 07 Greenwich time
(GMT), the first of these four violent explosions begun. A black
cloud of ash was initially observed. It rose 17 miles (27
kilometers) above Krakatoa. In the morning of the next day, on
August 27, 1883, at 05:30, 06:44 and 10:02 GMT, three more violent
eruptions occurred. It was the paroxysmal eruption which occurred at
10:02 which blew away the northern two-thirds of the island. This
was the most severe violent volcanic explosion on Earth in modern
times. The explosion was followed by the collapse of the unsupported
volcanic chambers of Krakatoa forming the huge underwater caldera.
It was this explosion and collapse of Krakatoa that generated
catastrophic tsunami waves as high as 37 meters. (120 ft.) that
caused havoc and destruction in the Sunda Strait."
Well as you can see from the initial early 1883
"large earthquake" a series of events unfolded that culminated in a
massive explosion at Krakatoa and a huge tsunamis on August 27th
1883. Thus it took about 7 months for the Krakatoa incident to fully
develop. Krakatoa also had a huge loss of life - if repeated today
the loss of life could be MUCH higher.
It is early days yet BUT I do not believe that the danger from this
Boxing Day Sumatra event has passed. The locality off NW Sumatra has
now demonstrated unprecedented seismic instability over a duration
of several days and the region has a VERY VIOLENT and well
documented quake-tsunamis-volcanic eruption history. Whatever
precipitated this disastrous event it is highly unlikely that it is
over and therefore danger remains.
Keep your wits about you since yet more massive quakes and/or
explosive volcanic eruptions and tsunamis may well occur over the
next few months (or year(s)) - NB these may NOT be limited to the
Indian Ocean region.
world chart of real time earthquakes
(click image right)
seems to indicate that fresh quakes are initiating in other stressed
parts of the planets crust - particularly along the New
Guinea-Japan-Alaska-California fault systems - probably in response
to the disequilibrium in the Earth's tectonic stress field created
by the 8.3r Macquarie Island quake and then the 9.1r Sumatra and
subsequent quakes. The next few weeks will be critical in developing
our understanding of this event. It will pay to keep abreast of this
unfolding seismic event for several months if not years.
If a new major quake-tsunamis happened today or tomorrow is there
any system in place to warn the relevant populations and get them
out of harms way ???
Even here in Perth - Western Australia no such warning system exists
yet. Sure radio etc. could give warnings but there are no evacuation
plans, sirens, nor established disaster alert procedures - certainly
none that 99% of the population are aware of. We need to educate
public NOW and set up an immediate warning system. If nothing is in
place here in a relatively developed society what about the rest of
the largely third world Indian ocean. A seismic event warning system
is an absolute MUST for the Indian Ocean. It should in fact be
mandatory for the entire planet. There is ample geological evidence
for previous catastrophic seismic related events just about where
ever we look AND these type of incidents were recorded by the
ancient Egyptians (33 known catastrophic events).
It will NOT cost much to develop, install, and operate such a system
(probably MUCH less than We spend every day in Iraq). It should be
rushed into operation NOW = THIS WEEK, as an ad hoc system, then
tuned up ASAP over future weeks. We are at continued MAJOR risk over
the next few months from possible developments resulting from this
Boxing Day Sumatra seismic event.
Such events WILL happen again - all be it most likely over long (say
100 year) time intervals but the cost is so high we MUST install
insurance procedures NOW.
This is something our governments and the UN should initiate